Perhaps you should try some spelling variations:
trung thuoc » trung thuc, trung quoc, trung hoc
hieu sach » chieu sach, hieu cach, dien sach
trong thu » trong nha
dung cong » dung trong
doc hieu » toc thieu, hoc thieu, hoc hien
cong tac » cong ty
tac van » tac vang, cac van, tac va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: doc hieu sach - sinh ((trung thuoc) or (trong thu)) dung cong tac van ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu sach - sinh ((trung thuoc) OR (trong thu)) dung cong tac van ban.
• Adding a wildcard symbol may retrieve word variants: doc hieu sach - sinh ((trung thuoc) or (trong thu)) dung cong tac van ban*.